Detailed seabed bathymetric data are needed to better understand our marine environment because models of seabed morphology derived from these data provide useful insights into physical processes that act on the seabed and the location of different types of seabed habitats. Lord Howe Island lies approximately 450km off the northern coast of New South Wales. It is a volcanic island with a fringing coral reef on its western shore, and a shallow (20 - 120 m) shelf surrounds the island. Bathymetry data are required in this area to help identify major seabed processes and habitats, especially relict reef structures, and to measure how well physical seabed properties act as surrogates of patterns of biodiversity on this mid-ocean carbonate shelf. The data are also required to enable modelling of tsunami as they interact with the shelf around the island and the coast. This report describes the methodology employed in creating detailed bathymetry data grids of the Lord Howe Island region. It covers data collection, quality control and gridding. Descriptions are provided of each dataset employed, the methods used to integrate the different datasets and the attributes of the new bathymetry models. Four new bathymetry grids are presented, including grids that integrate bathymetry with the island's topography.

The Australian Bathymetry and Topography (AusBathyTopo) Torres Strait dataset contains depth and elevation data compiled from all available data within the Torres Strait into a 30 m-resolution Digital Elevation Model (DEM). The Torres Strait lies at the northern end of the Great Barrier Reef (GBR), the largest coral reef ecosystem on Earth, and straddles the Arafura Sea to the west and the Coral Sea to the east. The Torres Strait area is bounded by Australia, Indonesia and Papua New Guinea. Bathymetry mapping of this extensive reef and shoal system is vital for the protection of the Torres Strait allowing for the safe navigation of shipping and improved environmental management. Over past ten years, deep-water multibeam surveys have revealed the highly complex continental slope canyons in deeper Coral Sea waters. Shallow-water multibeam surveys conducted by the US-funded Source-to-Sink program revealed the extensive Fly River delta deposits. Airborne LiDAR bathymetry acquired by the Australian Hydrographic Office cover most of the Torres Strait and GBR reefs, with coverage gaps supplemented by satellite derived bathymetry. The Geoscience Australia-developed National Intertidal DIgital Elevation Model (NIDEM) improves the source data gap along Australia’s vast intertidal zone. We acknowledge the use of the CSIRO Marine National Facility (https://ror.org/01mae9353 ) in undertaking this research.” The datasets used were collected by the Marine National Facility on 13 voyages (see Lineage for identification). All source bathymetry data were extensively edited as point clouds to remove noise, given a consistent WGS84 horizontal datum, and where possible, an approximate MSL vertical datum. The 30 m-resolution grid is a fundamental dataset to underpin marine habitat mapping, and can be used to accurately simulate water mixing within a whole-of-GBR scale hydrodynamic model. This dataset is not to be used for navigational purposes.

The Bass Strait Digital Elevation Model (DEM) is a compilation of all available bathymetry data for the area of seabed between the coastlines of Victoria and northern Tasmania, extending approximately 460 km from west of King Island to east of Flinders Island. The Bass Strait is bounded by a continental slope incised with numerous canyons, including the prominent Bass Canyon on the eastern side. The region encompasses islands and exposed rocks, drowned paleo-shorelines and dunefields, fringed by a rugged coastline. Bathymetry mapping of the seafloor is vital for the protection of Bass Strait, allowing for safe navigation of shipping, improved environmental management and resource development. Australian Hydrographic Office-supplied ENC tile spot depths were used to develop the general bathymetry variation across the entire region. Shallow- and deep-water multibeam survey data reveal the complexity of the seafloor for the continental shelf and adjacent canyons which incise the western and eastern sides of Bass Strait. Airborne LiDAR bathymetry acquired by the Australian Hydrographic Office cover most of the northern Tasmanian nearshore and coast, with some coverage gaps supplemented by Landsat-8 satellite derived bathymetry data. The Geoscience Australia-developed Intertidal Elevation Model DEM improves the source data over the intertidal zone. Highly accurate photogrammetry coastline data developed for the Tasmania, Victoria and New South Wales coastlines, and Near Surface Feature data representing shoal features observable in aerial imagery, were used to improve the land/water interface of the numerous island and rock features. All source bathymetry data were extensively edited as 3D point clouds to remove noise, given a consistent WGS84 horizontal datum, and where possible, an approximate MSL vertical datum.<p><p>This dataset is not to be used for navigational purposes.

The AusBathyTopo 250m (Australia) 2023 Grid is a high-resolution depth model for Australia that replaces the Australian Bathymetry and Topography Grid, June 2009. This publication is the result of a collaborative partnership between Geoscience Australia, the Australian Hydrographic Office, James Cook University, and the University of Sydney. It has been compiled using 1582 unique data sources from multibeam echosounders, single-beam echosounders, LiDAR, 3D seismic first returns, Electronic Navigation Charts and satellite derived bathymetry alongside higher-resolution regional compilations. In particular, the map incorporates new innovations such as the use of earth observation data (satellite based) produced by Digital Earth Australia to improve shallow coastal depth modelling to present a seamless transition between land and sea. All source bathymetry data were extensively edited as 3D point clouds to remove noise, given a consistent WGS84 horizontal datum, and where possible, an approximate MSL vertical datum. This new continental-scale grid represents decades of data collection, analysis, investment and collaboration from Australia’s seabed mapping community and is a significant improvement on the 2009 compilation. The data extends across a vast area from 92°E to 172° E and 8°S to 60° S. This includes areas adjacent to the Australian continent and Tasmania, and surrounding Macquarie Island and the Australian Territories of Norfolk Island, Christmas Island, and Cocos (Keeling) Islands. Australia's marine jurisdiction offshore from the territory of Heard and McDonald Islands and the Australian Antarctic Territory are not included. We acknowledge the use of the CSIRO Marine National Facility (https://ror.org/01mae9353 ) in undertaking this research. The datasets used were collected by the Marine National Facility on 43 voyages (see Lineage for identification). This dataset is not to be used for navigational purposes.

Christmas Island is located approximately 2,600 North West of Perth. It is the surface expression of an emergent seamount uplifted by tectonics. Bathymetry data are required in this area to help identify major seabed processes and habitats. The data are also required to enable modelling of tsunami as they interact with the shelf around the island and the coast. This report describes the methodology employed in creating detailed bathymetry data grids of the Christmas Island region. It covers data collection, quality control and gridding. Descriptions are provided of each dataset employed, the methods used to integrate the different datasets and the attributes of the new bathymetric models. Five new bathymetry grids are presented, including grids that integrate bathymetry with the island's topography.<p><p>This dataset is not to be used for navigational purposes.